Antimicrobial or antibiotic treatment is a well-accepted therapy for fighting microbial infections that takes advantage of the existence of biological processes that are unique to bacteria or fungi, that can be safely inhibited to the detriment of the bacteria, without producing undesired or harmful side effects in the individual receiving such therapy. However, due at least in part to the continual evolution of microbial resistance to the available classes of antibiotics, and in part to the recent slowdown in the introduction of novel antimicrobials to market, there exists a need for the development of screening assays that target previously unexploited biochemical systems in microbes. In particular, there exists the need for the identification of new bacterial targets for use in drug discover programs designed to identify agents having potential use as anti-infective agents with novel modes of actions.
The present invention is based at least in part, on the identification of a novel target for use in screening assays designed to identify antimicrobial agents. In particular, the present invention is based on the identification and characterization of a previously unidentified microbial pantothenate kinase gene, coax. The coaX gene was first identified in B. subtilis where it is one of two genes encoding functional pantothenate kinase. Initially the present inventors identified and cloned the B. subtilis coaA gene (previously termed yqjS) that encodes a pantothenate kinase homologous to the CoaA enzyme previously characterized in E. coli. A second gene (previously termed yacB) has also been identified and cloned by the present inventors that is not homologous to any previously described pantothenate kinase. This latter pantothenate kinase-encoding gene has been renamed coaX. The coax gene could be deleted from B. subtilis strains with an intact coaA gene, but it could not be deleted from a strain containing a deletion in the coaA gene, indicating that the coaX gene is not essential in B. subtilis strains with a wild-type coaA gene. Homologs of the coaX gene can be found in a number of bacterial species, including but not limited to Aquifex aeolicus, Bacillus anthracis, Bacillus halodurans, Bacillus stearothermophilus, Caulobacter crescentus, Chlorobium tepidum, Clostridium acetobutylicum, Dehalococcoides ethenogenes, Deinococcus radiodurans, Desulfovibrio vulgaris, Geobacter sulfurreducens, Pseudomonas putida, Rhodobacter capsulatus, Thiobacillus ferrooxidans, Streptomyces coelicolor, Synechocystis sp., Thermotoga maritima, Bordetella pertussis, Borrelia burgdorferi, Campylobacter jejuni, Clostridium difficile, Helicobacter pylori, Neisseria meningitidis, Neisseria gonorrhoeae, Porphyromonas gingivalis, Pseudomonas aeruginosa, Pseudomonas syringae pv tomato, Treponema pallidum, Xylella fastidiosa and Mycobacterium tuberculosis. More importantly, however, this novel pantothenate kinase gene has been found to be the sole essential pantothenate kinase in troublesome pathogens including, but not limited to, Bordetella pertussis, Borrelia burgdorferi, Campylobacter jejuni, Helicobacter pylori, Neisseria meningitidis, Pseudomonas aeruginosa, Treponema pallidum and Xylella fastidiosa. Accordingly, the coaX gene represents an attractive target for screening for new antibacterial compounds to combat these pathogenic microorganisms, particularly microorganisms in which coaX is the sole pantothenate kinase-encoding gene.
Accordingly, the present invention features isolated CoaX proteins, in particular, proteins encoded by the coax gene in bacteria. The invention also features isolated nucleic acid molecules and/or genes, e.g., bacterial nucleic acid molecules and/or genes, in particular, isolated bacterial coaX nucleic acid molecules and/or genes. Also featured are vectors that contain isolated coaX nucleic acid molecules and/or genes as well as mutant coaX nucleic acid molecules and/or genes. Also featured are recombinant microorganisms (e.g., microorganisms belonging to the genus Escherchia or Bacillus, for example, E. coli or B. subtilis) containing isolated coaX nucleic acid molecules and/or genes or mutant coaX nucleic acid molecules and/or genes of the present invention. In particular, the invention features recombinant microorganisms that produce the CoaX proteins of the present invention, e.g., pantohthenate kinase proteins encodes by the coaX nucleic acid molecules and/or genes of the present invention.
Also featured are methods for identifying CoaX modulators utilizing, for example, isolated CoaX proteins of the present invention or recombinant microorganisms expressing the CoaX proteins of the present invention.
Other features and advantages of the invention will be apparent from the following detailed description and claims.